As promised, here is another concept that is important to recognize and understand.
Advantage: The “4 P Principle”
When considering the application of advantage, the following principle is provided as a guideline for officials. Remember, advantage application may differ depending upon the skill level, age level, and general atmosphere of the game.
The “4 P Principle” of Advantage Application:
1. Possession of ball: control by team or player.
2. Potential for attack: ability to continue a credible and dangerous attack.
3. Personnel: skill of attackers, numerical advantage.
4. Proximity to opponent’s goal: closeness to goal.
For this concept its important to remember that "advantage application may differ depending upon the skill level, age level, and general atmosphere of the game." Skill level and age level are pretty easy to grasp; if you're doing a U9 game you probably won't be calling very many advantages. But what does "general atmosphere of the game" mean? Well, it can mean a lot of things and that's what makes advantage a tough one.
As a referee we must be able to read the game, understand how the players are feeling and see the potential for conflict before it happens. Yes, that's as difficult as it sounds. So when we are deciding whether or not to let play go without calling the foul, we need to consider the 4 P's as well as the "temperature" of the match. Read how the player who was fouled reacted to the incident: Did they understand your decision? Or are they getting up and looking to retaliate? A hotly contested game can explode if players feel they were cheated by a poor advantage call. Sometimes in those situations you'll want to lean towards simply calling the foul.
Remember, the beautiful thing about advantage is you can always bring it back. Take a view seconds, observe the situation and decide what to do. If it doesn't pan out the way you had hoped then blow the whistle and bring the ball back.